Conformational Plasticity of Centrin 1 from Toxoplasma gondii in Binding to the Centrosomal Protein SFI1

Biomolecules. 2022 Aug 13;12(8):1115. doi: 10.3390/biom12081115.

Abstract

Centrins are calcium (Ca2+)-binding proteins that are involved in many cellular functions including centrosome regulation. A known cellular target of centrins is SFI1, a large centrosomal protein containing multiple repeats that represent centrin-binding motifs. Recently, a protein homologous to yeast and mammalian SFI1, denominated TgSFI1, which shares SFI1-repeat organization, was shown to colocalize at centrosomes with centrin 1 from Toxoplasma gondii (TgCEN1). However, the molecular details of the interaction between TgCEN1 and TgSFI1 remain largely unknown. Herein, combining different biophysical methods, including isothermal titration calorimetry, nuclear magnetic resonance, circular dichroism, and fluorescence spectroscopy, we determined the binding properties of TgCEN1 and its individual N- and C-terminal domains to synthetic peptides derived from distinct repeats of TgSFI1. Overall, our data indicate that the repeats in TgSFI1 constitute binding sites for TgCEN1, but the binding modes of TgCEN1 to the repeats differ appreciably in terms of binding affinity, Ca2+ sensitivity, and lobe-specific interaction. These results suggest that TgCEN1 displays remarkable conformational plasticity, allowing for the distinct repeats in TgSFI1 to possess precise modes of TgCEN1 binding and regulation during Ca2+ sensing, which appears to be crucial for the dynamic association of TgCEN1 with TgSFI1 in the centrosome architecture.

Keywords: SFI1 protein; Toxoplasma gondii; calcium; centrin; protein-peptide interactions.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Sequence
  • Animals
  • Calcium / metabolism
  • Calcium-Binding Proteins / metabolism
  • Cell Cycle Proteins / metabolism
  • Mammals / metabolism
  • Protein Binding
  • Protein Conformation
  • Repressor Proteins / metabolism
  • Saccharomyces cerevisiae / metabolism
  • Saccharomyces cerevisiae Proteins* / metabolism
  • Toxoplasma* / metabolism

Substances

  • Calcium-Binding Proteins
  • Cell Cycle Proteins
  • Repressor Proteins
  • SFI1 protein, S cerevisiae
  • Saccharomyces cerevisiae Proteins
  • Calcium

Grants and funding

This research was supported by departmental funds provided by the Italian Ministry of Research and Education (FUR2020 to AA and PD), and in part by the Italian MIUR-PRIN 2017 grant No. 2017ZBBYNC (to AA).